When I was asked by the editors of the Financial Times to contribute to a series on the future of conservatism, I hesitated because it seemed to me that in both the US and Europe what was most needed was not a new form of conservatism but rather a reinvention of the left. For more than a generation we have been under the sway of conservative ideas, against which there has been little serious competition. In the wake of the financial crisis and the rise of massive inequality, there should be an upsurge of left-wing populism, and yet some of...